A GENERIC KEY TO THE PROTOZOEAN, MYSIS, AND POSTLARVAL STAGES 

 OF THE LITTORAL PENAEIDAE OF THE NORTHWESTERN GULF OF 

 MEXICO ' 



Harry L. Cook, Fishery Biologist (Research), Bureau of Commercial Fisheries Biological Laboratory 



Galveston, Tex. 



ABSTRACT 



An illustrated key presenting criteria for differentiat- 

 ing the stages and substages of Gulf of Mexico penaeid 

 larvae (and post larvae) from comparable stages of the 

 more common nonpenaeids is presented. A second key 



permits generic identification of penaeid protozoean, 

 mysis, and postlarval stages. All genera are illustrated, 

 and a table of important diagnostic characters is 

 included. 



Shrimp of the Family Penaeidae which support 

 valuable commercial fisheries in the northwestern 

 Gulf of Mexico are being studied comprehensively 

 by fishery scientists at the Bureau of Commerical 

 Fisheries Biological Laboratory in Galveston, Tex. 

 To properly manage such fisheries, it is necessary 

 to fully understand the dynamics of the shrimp 

 populations upon which they depend. This 

 capability requires, in turn, as complete a knowl- 

 edge as possible of the life history of the species 

 involved. 



Studies of the early (planktonic) life history of 

 the Gulf's commercially important shrimps have 

 been hampered by difficulties encountered in 

 distinguishing larvae of these species from those of 

 lesser importance. Fortunately, there has been 

 considerable research on the description and 

 general systematica of larval and postlarval 

 Penaeidae both in this country and abroad. As a 

 result, all the littoral genera known to occur in the 

 northwestern Gulf of Mexico have had representa- 

 tives — although not necessarily of indigenous 

 species — at least partially described. The princi- 

 pal problem, therefore, was one of consolidating all 



Note.— Approved for publication Sept. 17, 1964. 



1 Contribution No. 189, Bureau of Commercial Fisheries Biological Labora- 

 tory, Galveston, Tex. 



the available information and ascertaining what 

 portions of it might help describe the local penaeid 

 larvae. The intent of this paper is to present 

 criteria that will aid in distinguishing larvae and 

 postlarvae of the genus Penaeus Fabricius from 

 those of Parapenaeus Smith, Sicyonia H. Milne 

 Edwards, Solenocera Lucas, Trachypeneus Alcock, 

 and Xiphopeneus Smith, the five other littoral 

 genera found locally. 



The material made available for examination 

 during this study was collected systematically 

 between March 1959 and March 1960 and during 

 January to December 1961. From January to 

 September 1961, plankton was sampled with a 

 Gulf-V net to depths of 45 fathoms between Cam- 

 eron, La., and Freeport, Tex. In September, the 

 sampling program was enlarged to include the area 

 between Morgan City, La., and the mouth of the 

 Colorado River, Tex. 



Although various larval stages of several species 

 represented in this area had been recorded, there 

 were no established criteria for differentiating the 

 penaeid larvae. Consequently, as new or thereto- 

 fore unrecognized penaeid larvae and postlarvae 

 were found in the plankton samples, they were 

 assigned a code number and a reference sketch of 

 them was made. Through the use of descriptions 



FISHERY BULLETIN: VOLUME 65, NO. 2 



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